The present invention relates to a method of conveying and scanning photographic media, as well as a scanning apparatus which is adapted to scan photographic media.
A typical film scanner continuously scans film as it moves at a constant velocity through a film gate. In order to drive the film through the scanner as well as the film gate, conventional scanners use an arrangement of idler rollers and drive rollers which are operable to drive the film. The idler rollers and drive rollers form a nip therebetween through which the film is passed, grip the film and move it through the film gate. During this process and especially during the conveyance of the film, the idler and drive rollers tend to cause a disturbance of the film motion. That is, the idler and drive rollers may cause the film to bounce around in a number of directions. This film motion disturbance can result in a misregistration of the film at the film gate which can adversely affect image quality. More specifically, the leading and trailing edges of the film cause a disturbance in the film motion as they pass through the nip rollers which adversely affects image quality during scanning.
The present invention provides for a method of conveying and scanning photographic media, as well as a scanning apparatus which overcome the image quality drawbacks of conventional scanners as discussed above. In a first feature of the present invention, an arrangement is provided in which an idler roller of an idler roller and drive roller pair is lifted from the drive roller before the leading and trailing edges of the film passes over the drive roller, to thus minimize any disturbance of the film motion and therefore improve the image quality.
In a further feature of the invention, a continuous cam is used as a mechanism for lifting the idler roller from the drive roller.
In a still further feature of the invention, side plates are used to precisely position film within an optical path for proper scanning. The side plates can be adjustable to accommodate films of different widths and are adjusted by way of a lead screw. In this further feature of the present invention, a coupler with linear play is used to couple a drive means which has a motor to the lead screw. The coupling permits the lead screw to keep turning when one side plate hits a stop before the other side plate, so that the lead screw can move the other side plate to its intended position. With this arrangement, it is not necessary to precisely position the side plates during assembly of the scanner.
The present invention therefore provides for a method of conveying photographic media to be scanned through a scanner. The method comprises the steps of placing an entrance roller pair located at an entrance of the scanner in an engaged position and an exit roller pair located at an exit of the scanner in a disengaged position during an idle period of the scanner; maintaining the engaged position of the entrance roller pair and the disengaged position of the exit roller pair as a leading edge of photographic media in a media path of the scanner passes an entrance sensor, with the entrance sensor being located at an entrance of the scanner and upstream of the entrance roller pair with respect to a direction of travel of the media in the media path; maintaining the engaged position of the entrance roller pair and placing the exit roller pair in an engaged position when a leading edge of the media in the media path passes the exit sensor, with the exit sensor being located at the exit of the scanner and downstream of the exit roller pair with respect to the direction of travel of the media; and placing the entrance roller pair in a disengaged position and maintaining the engaged position of the exit roller pair when a trailing edge of the media reaches the entrance sensor.
The present invention further relates to a scanner that comprises a media path for photographic media to be scanned; an entrance sensor provided at an entrance of the scanner for sensing at least a leading edge or a trailing edge of photographic media as it travels along the media path; an entrance roller pair provided downstream of the first sensor with respect to a direction of travel of the media along the path, with the entrance roller pair comprising an entrance drive roller and an entrance idler roller which are in an engaged position during an idle state of the scanner; an exit roller pair provided downstream of the entrance roller pair with respect to the direction of travel, with the exit roller pair being located in a vicinity of an exit of the scanner, and the exit roller pair comprising an exit drive roller and an exit idler roller which are in a disengaged position during an idle state of the scanner; an exit sensor provided at the exit of the scanner for sensing at least the leading edge or the trailing edge of the media as it travels along the media path; and a controller adapted to receive signals from at least one of the entrance sensor and the exit sensor during a scanning of photographic media in the media path, to place the exit idler roller and the exit drive roller in an engaged position when the leading edge of the media passes the exit sensor and place the entrance idler roller and the entrance drive roller in a disengaged position when the trailing edge of the media passes the entrance sensor.
The present invention further relates to a scanner that comprises a media path for media to be scanned; and at least one roller pair comprising an idler roller and a drive roller for conveying media along the media path, with the idler roller being mounted on a rotatable continuous cam shaft. The continuous cam shaft is rotatable between at least a first position where the cam shaft moves the idler roller relative to the drive roller to form a nip with the drive roller for the passage of media therebetween, and a second position where the cam shaft moves the idler roller away from the drive roller so that only the drive roller contacts the media in the media path.
The present invention further relates to a scanner which comprises a media path for media to be scanned; at least one roller pair comprising an idler roller and a drive roller for conveying media along the media path; sensing means for sensing a passage of media along the media path; and moving means for moving the idler roller relative to the drive roller in response to a signal from the sensing means, with the moving means moving the idler roller relative to the drive roller between a first position in which the idler roller forms a nip with the drive roller and a second position in which the idler roller moves away from the drive roller.